The present invention is concerned with a method of manufacturing cellulose pulp from ligno-cellulose material wherein the material is ground in a mill which is subjected to internal steam pressure. The invention is further concerned with means for the implementation of the method.
In such manufacture of cellulose pulp, especially for paper making, it is necessary in order for the pulp to be used efficiently that said pulp consist of a uniform fibre fraction without oversize non-comminuted (non-defibrated) knots or bundles of fibres. In conventional pulp manufacture this is achieved by slurrying the manufactured pulp with water, whereafter it is caused to pass in the form of a relatively thin suspension through a variety of fibre sorting means such as screens equipped with perforated or slotted plates for the removal of shives, or so-called hydrocyclones wherein the stock is cleaned of shives and insufficiently comminuted (defibrated) bundles of fibres by centrifugal action.
All these so-called water-dependent systems suffer from the drawback of requiring large quantities of water, in the order of 1:300 to 1:100, which water must be removed in subsequent treatment before the pulp is transported to the point of use, baled, etc. The suspension of the pulp in water and the transportation of the large volumes of liquid to screens and, hydrocyclones takes a great deal of energy, and moreover, the oversize bundles of fibres or shives removed in the screens and hydrocyclones must be dewatered again to a concentration of approximately 1:2 to 1:4 for efficient further treatment thereof.